Supramaximal Testing to Confirm the Achievement of VO2max in Acute Hypoxia

To confirm maximal oxygen uptake ( VO2max), a bout of supramaximal exercise can be performed after maximal exercise. Supramaximal exercise verifies VO(2max )if the VO(2max )is similar to the incremental test. Acute hypoxia decreases VO(2max )because of decreases in arterial oxygenation, which results in different determinants of VO2max.Purpose:We sought to determine if supramaximal exercise testing confirms the achievement of VO(2max)in acute hypoxia. We hypothesized that the incremental and supramaximal VO(2)will be sufficiently similar in acute hypoxia. Methods: Twenty-one healthy adults (males n= 13, females n= 8) completed incremental and supramaximal exercise tests in normoxia and acute hypoxia (fraction inspired oxygen = 0.14) separated by at least 48 h. Incremental exercise started at 80 and 60 W innormoxia and 40 and 20 W in hypoxia for males and females, respectively, with all increasing by 20 W each minute until volitional exhaustion. After a 20-min postexercise rest period, a supramaximal test at 110% peak power until volitional exhaustion was completed. Results: Supramaximal exercise testing yielded a lower VO2than incremental testing in hypoxia (3.11 +/- 0.78 vs 3.21 +/- 0.83 L<middle dot>min-1,P= 0.001)and normoxia (3.71 +/- 0.91 vs 3.80 +/- 1.02 L<middle dot>min(-1),P= 0.01). Incremental and supramaximal VO(2 )were statistically similar, using investigator-determined equivalence bounds +/- 150 mL<middle dot>min(-1), in hypoxia (P= 0.02, 90% confidence interval [CI] = 0.05-0.14) and normoxia(P= 0.03, 90% CI = 0.01-0.14). Likewise, using +/- 2.1 mL<middle dot>kg(-1)<middle dot>min(-1)bounds, incremental and supramaximal VO2values were statistically similar in hypoxia (P=0.04,90%CI=0.70-2.0) and normoxia (P= 0.04, 90% CI = 0.30-2.0).Conclusions: Despite differences in the oxygen cascade, incremental and supramaximal VO(2)values were statistically similar in both hypoxia and normoxia, demonstrating the utility of supramaximal verification of VO(2max )in the setting of acute hypoxia